I hear ya and while I was going to do inline, I later decided to bypass with a larger unit than I had originally planned.
As mentioned in my build thread, I can easily incorporate the factory cooler if desired later. With realtime ATF temps, I will monitor, and view this as an experiment of sorts...
Thus far, my ATF has seen much lower average and peak temps. The high is in the low 170s, and I purposely left OD on to reach that temp (was curious how high it would go). The average or vast majority of driving has seen temps in the 130 to 150 range.
I of course realize that higher ambient temps, along high load, low speed situations will tax it to where it can see undesirable temps. However, I'm feeling pretty convinced that a little fan will do the trick and I had already did a test fit, mock-up during the install.
From the accounts of others, and through what little experience I have so far, I believe the cooler I installed, bypassed, with select use of OD, will keep temps in a happy zone the vast majority of the time...